1. Field of the Invention
The present invention relates to a battery cooling apparatus for cooling battery cells housed in a case.
2. Description of Related Art
It is known to cool battery cells housed in a case using a battery cooling apparatus. For example, refer to Japanese Patent Application Laid-open No. 2010-50000 (Patent document 1) and Japanese Patent Application Laid-open No. 2004-288527 (Patent document 2).
The battery cooling apparatus described in Patent document 1 includes a cooling plate disposed so as to be in contact with a battery block of battery cells. The cooling plate has a hollow part which is filled with cooling liquid, and is provided with a heat exchanger. The heat exchanger is connected with a coolant passage through which a coolant is supplied. The heat exchanger is cooled by the vaporization heat of the coolant to cool the cooling liquid so that the battery cells are cooled by the cooling plate.
The battery cooling apparatus described in Patent document 2 includes a battery assembly having a heat transfer medium passage for passing heat transfer medium between single batteries, a feed means for feeding the heat transfer medium, a feed passage for supplying the heat transfer medium to the heat transfer medium passage, and a discharge passage for discharging the heat transfer medium from the heat transfer medium passage. The battery assembly, feed means, feed passage and discharge passage are provided in a case. The heat transfer medium fed by the feed means flows through the feed passage, heat transfer medium passage and discharge passage in this order, and returns to the feed means. The heat transfer medium flows through a closed circuit while cooling the single batteries.
However, the battery cooling apparatus described in Patent document 1 has a problem in that since the batteries are cooled by the vaporization heat of the coolant using refrigeration cycle equipment, the manufacturing cost is high. In a case where the refrigeration cycle equipment is housed in the case that houses the batteries, since a tube for passing the coolant has to be provided inside the case, the manufacturing cost further increases.
The battery cooling apparatus described in Patent document 2 has the structure in which the batteries are disposed in a closed space within the case so that the temperature of the batteries can be adjusted by circulating the heat transfer medium in a closed circuit. Accordingly, since heat dissipation from inside the case to outside the case is performed only by natural convection of the circulating heat transfer medium, it is difficult to sufficiently cool the batteries.
If the battery cooling apparatus described in Patent document 2 is modified to employ a non-circulation method in which the batteries are cooled by air sucked from outside the case, and the air having cooled the batteries is discharged to outside the case, there arises another problem that noise easily propagates to the outside because the cooling passage is open to the outside of the case. Further, in this case, dust can easily enter the case, and dew condensation easily occurs inside the case. In addition, it is necessary to take measures of reducing effects of discharged air flow on the ambient environment.